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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Evaluation of Candidate Materials for a High-Temperature Stirling Convertor Heater Head

The Department of Energy (DOE) and NASA have identified Stirling Radioisotope Generators (SRG) as a candidate power system for use on long-duration, deep-space science missions and Mars rovers. One of the developments planned for an upgraded version of the current SRG design is to achieve higher efficiency by increasing the overall operating temperature of the system. Currently, the SRG operates with a heater head temperature of 650 C and is fabricated from the nickel base superalloy 718. This temperature is at the limit of Alloy 718's capability, and any planned increase in temperature will be contingent on identifying a more capable material from which to fabricate the heater head. To this end, an assessment of material candidates was performed assuming a range of heater head temperatures. The chosen alternative material candidates will be discussed, along with the development efforts needed to ensure that these materials can meet the demanding system requirements of long-duration operation in hostile environments.

Bowman, Randy↗
NASA NTRS2008

ART: Surveying the Local Universe at 2-11 keV

The Astronomical Rontgen Telescope (ART) is a medium-energy x-ray telescope system proposed for the Russian-led mission Spectrum Rontgen-Gamma (SRG). Optimized for performance over the 2-11-keV band, ART complements the softer response of the SRG prime instrument-the German eROSITA x-ray telescope system. The anticipated number of ART detections is 50,000-with 1,000 heavily-obscured (N(sub H)> 3x10(exp 23)/sq cm) AGN-in the SRG 4-year all-sky survey, plus a comparable number in deeper wide-field (500 deg(sup 2) total) surveys. ART's surveys will provide a minimally-biased, nearly-complete census of the local Universe in the medium-energy x-ray band (including Fe-K lines), at CCD spectral resolution. During long (approx.100-ks) pointed observations, ART can obtain statistically significant spectral data up to about 15 keY for bright sources and medium-energy x-ray continuum and Fe-K-line spectra of AGN detected with the contemporaneous NuSTAR hard-x-ray mission.

O'Dell, S. L.↗
DOE OSTI2022

The eROSITA Final Equatorial-Depth Survey (eFEDS): Identification and characterization of the counterparts to point-like sources

In November 2019, eROSITA on board of the Spektrum-Roentgen-Gamma (SRG) observatory started to map the entire sky in X-rays. After the four-year survey program, it will reach a flux limit that is about 25 times deeper than ROSAT. During the SRG performance verification phase, eROSITA observed a contiguous 140 deg 2 area of the sky down to the final depth of the eROSITA all-sky survey (eROSITA Final Equatorial-Depth Survey; eFEDS), with the goal of obtaining a census of the X-ray emitting populations (stars, compact objects, galaxies, clusters of galaxies, and active galactic nuclei) that will be discovered over the entire sky. This paper presents the identification of the counterparts to the point sources detected in eFEDS in the main and hard samples and their multi-wavelength properties, including redshift. To identify the counterparts, we combined the results from two independent methods (NWAY and ASTROMATCH), trained on the multi-wavelength properties of a sample of 23k XMM-Newton sources detected in the DESI Legacy Imaging Survey DR8. Then spectroscopic redshifts and photometry from ancillary surveys were collated to compute photometric redshifts. Of the eFEDS sources, 24 774 of 27 369 have reliable counterparts (90.5%) in the main sample and 231 of 246 sources (93.9%) have counterparts in the hard sample, including 2514 (3) sources for which a second counterpart is equally likely. By means of reliable spectra, Gaia parallaxes, and/or multi-wavelength properties, we have classified the reliable counterparts in both samples into Galactic (2695) and extragalactic sources (22 079). For about 340 of the extragalactic sources, we cannot rule out the possibility that they are unresolved clusters or belong to clusters. Inspection of the distributions of the X-ray sources in various optical/IR colour-magnitude spaces reveal a rich variety of diverse classes of objects. The photometric redshifts are most reliable within the KiDS/VIKING area, where deep near-infrared data are also available. This paper accompanies the eROSITA early data release of all the observations performed during the performance and verification phase. Together with the catalogues of primary and secondary counterparts to the main and hard samples of the eFEDS survey, this paper releases their multi-wavelength properties and redshifts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Benchmark neutrinoless double- β decay matrix elements in a light nucleus

We compute nuclear matrix elements of neutrinoless double-β decay mediated by light Majorana-neutrino exchange in the $\textit{A}$ = 6 system. The goal for this work is to benchmark two many-body approaches, the no-core shell model and the multireference in-medium similarity renormalization group (SRG). We use a SRG-evolved next-to-next-to-next-to-leading chiral order two-body potential for the nuclear interaction, and make the approximation that the isospin is conserved. We compare the results of the two approaches as a function of the cutoff on the many-body basis space. Although differences are seen in the predicted nuclear radii, the ground-state energies and neutrinoless double-β decay matrix elements produced by the two approaches show significant agreement. We discuss the implications for calculations in heavier nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Quasi-deuteron model at low renormalization group resolution

The quasi-deuteron model introduced by Levinger is used to explain cross sections for knocking out high-momentum protons in photoabsorption on nuclei. This is within a framework we characterize as exhibiting high renormalization group (RG) resolution. Assuming a one-body reaction operator, the nuclear wave function must include two-body short-range correlations (SRCs) with deuteronlike quantum numbers. In Phys. Rev. C 104, 034311 (2021), we showed that SRC physics can be naturally accounted for at low RG resolution. We describe the quasi-deuteron model at low RG resolution and determine the Levinger constant, which is proportional to the ratio of nuclear photoabsorption to that for photodisintegration of a deuteron. We extract the Levinger constant based on the ratio of momentum distributions at high relative momentum. We compute momentum distributions evolved under similarity RG (SRG) transformations where the SRC physics is shifted into the operator as a universal two-body term. The short-range nature of this operator motivates using local-density approximations with uncorrelated wave functions in evaluating nuclear matrix elements, which greatly simplifies the analysis. The operator must be consistently matched to the RG scale and scheme of the interaction for a reliable extraction. We apply SRG transformations to different nucleon-nucleon (NN) interactions and use the deuteron wave functions and Weinberg eigenvalues to determine approximate matching scales. We predict the Levinger constant for several NN interactions and a wide range of nuclei comparing to experimental extractions. The predictions at low RG resolution are in good agreement with experiment when starting with a hard NN interaction and the initial operator. Similar agreement is found using soft NN interactions when the additional two-body operator induced by evolution from hard to soft is included.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1992

X-ray scattering measurements from thin foil X-ray mirrors

Thin foil X-ray mirrors are to be used as the reflecting elements in the telescopes of the X-ray satellites Spectrum-X-Gamma (SRG) and ASTRO-D. High resolution X-ray scattering measurements from the Au coated and dip-lacquered Al foils are presented. These were obtained from SRG mirrors positioned in a test quadrant of the telescope structure and from ASTRO-D foils held in a simple fixture. The X-ray data is compared with laser data and other surface structure data such as STM, atomic force microscopy (AFM), TEM, and electron micrography. The data obtained at Cu K-alpha(1), (8.05 keV) from all the mirrors produced on Al foils shows a scatter which limits the obtainable half-power width to above 1.5 arcmin. Mirrors based on electroformed Ni foils, however, show local regions with a factor of 4 better performance, and they are being developed for future applications.

Christensen, F. E.↗
NASA NTRS2001

Stirling Technology Development at NASA GRC

The Department of Energy, Stirling Technology Company (STC), and NASA Glenn Research Center (NASA Glenn) are developing a free-piston Stirling convertor for a high efficiency Stirling Radioisotope Generator (SRG) for NASA Space Science missions. The SRG is being developed for multimission use, including providing electric power for unmanned Mars rovers and deep space missions. NASA Glenn is conducting an in-house technology project to assist in developing the convertor for space qualification and mission implementation. Recent testing of 55-We Technology Demonstration Convertors (TDCs) built by STC includes mapping of a second pair of TDCs, single TDC testing, and TDC electromagnetic interference and electromagnetic compatibility characterization on a nonmagnetic test stand. Launch environment tests of a single TDC without its pressure vessel to better understand the convertor internal structural dynamics and of dual-opposed TDCs with several engineering mounting structures with different natural frequencies have recently been completed. A preliminary life assessment has been completed for the TDC heater head, and creep testing of the IN718 material to be used for the flight convertors is underway. Long-term magnet aging tests are continuing to characterize any potential aging in the strength or demagnetization resistance of the magnets used in the linear alternator (LA). Evaluations are now beginning on key organic materials used in the LA and piston/rod surface coatings. NASA Glenn is also conducting finite element analyses for the LA, in part to look at the demagnetization margin on the permanent magnets. The world's first known integrated test of a dynamic power system with electric propulsion was achieved at NASA Glenn when a Hall-effect thruster was successfully operated with a free-piston Stirling power source. Cleveland State University is developing a multidimensional Stirling computational fluid dynamics code to significantly improve Stirling loss predictions and assist in identifying convertor areas for further improvements. This paper will update the status and results for these efforts.

Thieme, Lanny G.↗
NASA NTRS2002

Stirling Technology Development at NASA GRC

The Department of Energy, Stirling Technology Company (STC), and NASA Glenn Research Center (NASA Glenn) are developing a free-piston Stirling convertor for a high-efficiency Stirling Radioisotope Generator (SRG) for NASA Space Science missions. The SRG is being developed for multimission use, including providing electric power for unmanned Mars rovers and deep space missions. NASA Glenn is conducting an in-house technology project to assist in developing the convertor for space qualification and mission implementation. Recent testing, of 55-We Technology Demonstration Convertors (TDC's) built by STC includes mapping, of a second pair of TDC's, single TDC testing, and TDC electromagnetic interference and electromagnetic compatibility characterization on a nonmagnetic test stand. Launch environment tests of a single TDC without its pressure vessel to better understand the convertor internal structural dynamics and of dual-opposed TDC's with several engineering mounting structures with different natural frequencies have recently been completed. A preliminary life assessment has been completed for the TDC heater head, and creep testing of the IN718 material to be used for the flight convertors is underway. Long-term magnet aging tests are continuing to characterize any potential aging in the strength or demagnetization resistance of the magnets used in the linear alternator (LA). Evaluations are now beginning on key organic materials used in the LA and piston/rod surface coatings. NASA Glenn is also conducting finite element analyses for the LA, in part to look at the demagnetization margin on the permanent magnets. The world's first known integrated test of a dynamic power system with electric propulsion was achieved at NASA Glenn when a Hall-effect thruster was successfully operated with a free-piston Stirling power source. Cleveland State University is developing a multidimensional Stirling computational fluid dynamics code to significantly improve Stirling loss predictions and assist in identifying convertor areas for further improvements. This paper will update the status and results for these efforts.

Thieme, Lanny G.↗
NASA NTRS2002

Impact Testing of a Stirling Converter's Linear Alternator

The U.S. Department of Energy (DOE), in conjunction with the NASA John H. Glenn Research Center and Stirling Technology Company, are currently developing a Stirling convertor for a Stirling Radioisotope Generator (SRG). NASA Headquarters and DOE have identified the SRG for potential use as an advanced spacecraft power system for future NASA deep-space and Mars surface missions. Low-level dynamic impact tests were conducted at NASA Glenn Research Center's Structural Dynamics Laboratory as part of the development of this technology. The purpose of this test was to identify dynamic structural characteristics of the Stirling Technology Demonstration Convertor (TDC). This paper addresses the test setup, procedure, and results of the impact testing conducted on the Stirling TDC in May 2001.

Suarez, Vicente J.↗
NASA NTRS2003

Vibration Modal Characterization of a Stirling Convertor via Base-Shake Excitation

The U.S. Department of Energy (DOE), Lockheed Martin (LM), Stirling Technology Company (STC), and NASA John H. Glenn Research Center (GRC) are currently developing a high-efficiency Stirling convertor for use in a Stirling Radioisotope Generator (SRG). NASA and DOE have identified the SRG for potential use as an advanced power system for future NASA Space Science missions, providing spacecraft onboard electric power for deep space missions and power for unmanned Mars rovers. Low-level, baseshake sine vibration tests were conducted on the Stirling Technology Demonstration Convertor (TDC), at NASA GRC's Structural Dynamics Laboratory, in February 2001, as part of the development of this Stirling technology. The purpose of these tests was to provide a better understanding of the TDC's internal dynamic response to external vibratory base excitations. The knowledge obtained can therein be used to help explain the success that the TDC enjoyed in its previous random vibration qualification tests (December 1999). This explanation focuses on the TDC s internal dynamic characteristics in the 50 to 250 Hz frequency range, which corresponds to the maximum input levels of its qualification random vibration test specification. The internal dynamic structural characteristics of the TDC have now been measured in two separate tests under different motoring and dynamic loading conditions: (1) with the convertor being electrically motored, under a vibratory base-shake excitation load, and (2) with the convertor turned off, and its alternator internals undergoing dynamic excitation via hammer impact loading. This paper addresses the test setup, procedure and results of the base-shake vibration testing conducted on the motored TDC, and will compare these results with those results obtained from the dynamic impact tests (May 2001) on the nonmotored TDC.

Suarez, Vicente J.↗
NASA NTRS2004

Overview of NASA GRC Stirling Technology Development

The Stirling Radioisotope Generator (SRG) is currently being developed by Lockheed Martin Astronautics (LMA) under contract to the Department of Energy (DOE). The generator will be a high efficiency electric power source for NASA Space Science missions with the ability to operate in vacuum or in an atmosphere such as on Mars. High efficiency is obtained through the use of free-piston Stirling power conversion. Power output will be greater than 100 watts at the beginning of life with the decline in power largely due to the decay of the plutonium heat source. In support of the DOE SRG project, the NASA Glenn Research Center (GRC) has established a technology effort to provide data to ensure a successful transition to flight for what will be the first dynamic power system in space. Initially, a limited number of areas were selected for the effort, however this is now being expanded to more thoroughly cover key technical issues. There is also an advanced technology effort that is complementary to the near-term technology effort. Many of the tests use the 55-We Technology Demonstration Convertor (TDC). There have been multiple controller tests to support the LMA flight controller design effort. Preparation is continuing for a thermal/vacuum system demonstration. A pair of flight prototype TDC s have been placed on continuous operation. Heater head life assessment continues, with the material data being refined and the analysis moving toward the system perspective. Magnet aging tests continue to characterize any possible aging in the strength or demagnetization resistance of the magnets in the linear alternator. A reliability effort has been initiated to help guide the development activities with focus on the key components and subsystems. This paper will provide an overview of some of the GRC technical efforts, including the status, and a description of future efforts.

Schreiber, Jeffrey G.↗
NASA NTRS2004

Multi-d CFD Modeling of a Free-piston Stirling Convertor at NASA Glenn

A high efficiency Stirling Radioisotope Generator (SRG) is being developed for possible use in long duration space science missions. NASA s advanced technology goals for next generation Stirling convertors include increasing the Carnot efficiency and percent of Carnot efficiency. To help achieve these goals, a multidimensional Computational Fluid Dynamics (CFD) code is being developed to numerically model unsteady fluid flow and heat transfer phenomena of the oscillating working gas inside Stirling convertors. Simulations of the Stirling convertors for the SRG will help characterize the thermodynamic losses resulting from fluid flow and heat transfer between the working gas and solid walls. The current CFD simulation represents approximated 2-dimensional convertor geometry. The simulation solves the Navier Stokes equations for an ideal helium gas oscillating at low speeds. The current simulation results are discussed.

Wilson, Scott D.↗
NASA NTRS2004

Benchmark Tests for Stirling Convertor Heater Head Life Assessment Conducted

A new in-house test capability has been developed at the NASA Glenn Research Center, where a critical component of the Stirling Radioisotope Generator (SRG) is undergoing extensive testing to aid the development of analytical life prediction methodology and to experimentally aid in verification of the flight-design component's life. The new facility includes two test rigs that are performing creep testing of the SRG heater head pressure vessel test articles at design temperature and with wall stresses ranging from operating level to seven times that (see the following photograph).

Krause, David L.↗
NASA NTRS2005

Candidate Materials Evaluated for a High-Temperature Stirling Convertor Heater Head

The Department of Energy and NASA have identified Stirling Radioisotope Generators (SRGs) as a candidate power system for use on long-duration, deep-space science missions and Mars rovers. One of the developments planned for an upgraded version of the current SRG design is to achieve higher efficiency by increasing the overall operating temperature of the system. Currently, the SRG operates with a heater head temperature of 650 C and is fabricated from the nickel-base superalloy 718. The current operating temperature is at the limit of alloy 718 s capability, and any planned increase in temperature will be contingent on identifying a more capable material from which to fabricate the heater head. To this end, personnel at the NASA Glenn Research Center are evaluating advanced materials for a high-temperature heater head to allow a higher convertor temperature ratio and, thus, increase the system efficiency. A generic list of properties that were used to screen the candidate materials follows: (1) creep, (2) fabricability, (3) helium gas containment, (4) long-term stability and compatibility, (5) ability to form a hermetical closeout seal, and (6) ductility and toughness.

Bowman, Randy R.↗
NASA NTRS2005

Benchmark Calibration Tests Completed for Stirling Convertor Heater Head Life Assessment

A major phase of benchmark testing has been completed at the NASA Glenn Research Center (http://www.nasa.gov/glenn/), where a critical component of the Stirling Radioisotope Generator (SRG) is undergoing extensive experimentation to aid the development of an analytical life-prediction methodology. Two special-purpose test rigs subjected SRG heater-head pressure-vessel test articles to accelerated creep conditions, using the standard design temperatures to stay within the wall material s operating creep-response regime, but increasing wall stresses up to 7 times over the design point. This resulted in well-controlled "ballooning" of the heater-head hot end. The test plan was developed to provide critical input to analytical parameters in a reasonable period of time.

Krause, David L.↗
NASA NTRS2005

Utilizing Radioisotope Power Systems for Human Lunar Exploration

The Vision for Space Exploration has a goal of sending crewed missions to the lunar surface as early as 2015 and no later than 2020. The use of nuclear power sources could aid in assisting crews in exploring the surface and performing In-Situ Resource Utilization (ISRU) activities. Radioisotope Power Systems (RPS) provide constant sources of electrical power and thermal energy for space applications. RPSs were carried on six of the crewed Apollo missions to power surface science packages, five of which still remain on the lunar surface. Future RPS designs may be able to play a more active role in supporting a long-term human presence. Due to its lower thermal and radiation output, the planned Stirling Radioisotope Generator (SRG) appears particularly attractive for manned applications. The MCNPX particle transport code has been used to model the current SRG design to assess its use in proximity with astronauts operating on the surface. Concepts of mobility and ISRU infrastructure were modeled using MCNPX to analyze the impact of RPSs on crewed mobility systems. Strategies for lowering the radiation dose were studied to determine methods of shielding the crew from the RPSs.

Schreiner, Timothy M.↗
NASA NTRS2006

Update on Extended Operation of Stirling Convertors in Thermal Vacuum at NASA Glenn Research Center

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems (LMSS), Infinia Corporation, and NASA Glenn Research Center (GRC) have been developing a Stirling Radioisotope Generator (SRG) for use as a power system on space science missions. This generator would make use of Stirling cycle energy conversion to achieve higher efficiency than currently used alternatives. A test has been initiated at GRC to demonstrate functionality of Stirling conversion in a thermal vacuum environment over an extended period of time. The test article resembles the configuration of the SRG, but was designed without the requirement of low mass. Throughout the 8700 cumulative hours of operation, modifications to the supporting hardware were required to attain the desired operating conditions. These modifications, the status of testing, and the data recorded will be discussed in this paper.

Oriti, Salvatore M.↗
NASA NTRS2007

NASA's RPS Design Reference Mission Set for Solar System Exploration

NASA's 2006 Solar System Exploration (SSE) Strategic Roadmap identified a set of proposed large Flagship, medium New Frontiers and small Discovery class missions, addressing key exploration objectives. These objectives respond to the recommendations by the National Research Council (NRC), reported in the SSE Decadal Survey. The SSE Roadmap is down-selected from an over-subscribed set of missions, called the SSE Design Reference Mission (DRM) set. Missions in the Flagship and New Frontiers classes can consider Radioisotope Power Systems (RPSs), while small Discovery class missions are not permitted to use them, due to cost constraints. In line with the SSE DRM set and the SSE Roadmap missions, the RPS DRM set represents a set of missions, which can be enabled or enhanced by RPS technologies. At present, NASA has proposed the development of two new types of RPSs. These are the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), with static power conversion; and the Stirling Radioisotope Generator (SRG), with dynamic conversion. Advanced RPSs, under consideration for possible development, aim to increase specific power levels. In effect, this would either increase electric power generation for the same amount of fuel, or reduce fuel requirements for the same power output, compared to the proposed MMRTG or SRG. Operating environments could also influence the design, such that an RPS on the proposed Titan Explorer would use smaller fins to minimize heat rejection in the extreme cold environment; while the Venus Mobile Explorer long-lived in-situ mission would require the development of a new RPS, in order to tolerate the extreme hot environment, and to simultaneously provide active cooling to the payload and other electric components. This paper discusses NASA's SSE RPS DRM set, in line with the SSE DRM set. It gives a qualitative assessment regarding the impact of various RPS technology and configuration options on potential mission architectures, which could support NASA's RPS technology development planning, and provide an understanding of fuel need trades over the next three decades.

solar system↗